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Author Topic: 10m vertical  (Read 8991 times)
STAYVERTICAL
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Posts: 875




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« Reply #30 on: October 23, 2012, 05:46:17 PM »

I didn't mean to start an argument about theoretical antenna gain, I was merely responding to the OP about using a vertical for "local" contacts. Horizontal polarization is better for local contacts because most hams are using beams on 10 meters. For my installation, I found on 10 meter DX only, the HS6V vertical was getting better signal reports 2 out of 3 times compared to my crappy 3 element beam. It was not a recommendation for a vertical; only what worked and didn't work at my location.

Forty some years ago while I was a green and working in R&D, I ate humble pie on a regular basis when theory didn't always work out as expected. We all found a tech with practical experience was an asset to have around. With every environment came new challenges and answers.

Eznec and other programs based on free space physics with human introduced adjustments can be a valuable tool but not always predictable in a real world installation. I still recommend having multiple antenna types for all bands, because in any given situation, they may not perform as expected. HAM radio is full of surprises.     

Don't sweat it, the most accurate thing one can say about their antenna, is that at my qth this works better than that.
The list of my previous antenna's reads like a list of hollywood wives, or politicians lies, but I now know what works here and what doesn't.
For some reason of topography, verticals really excel at my qth (rocky hilltop).
Magnetic loops work really well too (vertically oriented), although dipoles seem to work "OK" - go figure.
So, theory aside, I do what works from experiment.

If the results change, I will adapt and try some other configuration - that's about the best anyone can do.
There is no point in going down with the ship muttering "but in theory it should ... gurgle gurgle).

Happy hamming, 73 - Rob
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KA7NIQ
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Posts: 258


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« Reply #31 on: October 23, 2012, 08:37:51 PM »

Hey Rob, ever tried a vertically polarized Delta Loop ?
Back when I lived in Seattle, I was blessed with two good sized trees.
I made a vertical delta loop for 80 that really played well.
Of course, it was fixed, but for a cheap antenna, erected in one day, it exceeded all my expectations.

I have done "crazy stuff" too. I once made what I called a "talking tree" at another QTH in Washington.

I threw some fishing line over top of the 2 trees, tied the wire to it,  and made a large vertical oriented loop. I fed it with 450 ohm line, initially at the bottom of the loop.  Then, I carefully pulled on the wire, and was able to get the feed point almost up on the top of the 85 foot trees!

The wire was insulated, and only tree limbs and branches supported it.
It did not stay up too long of course, maybe 4 to 6 months ? But It was sort of a flamethrower for DX on 40 and 80.

Of course, with my big Johnson matchbox, it loaded up easily on all hf bands, except 160. From 20 meters up, it was weird. It was deaf, much of the time. Except if a station just happened to be in the path of one of the lobes.

Of course, I also had a National NCL 2000 (remember them?) back then. I seldom had to wait in any 40 and 80 meter DX Pileups.

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STAYVERTICAL
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Posts: 875




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« Reply #32 on: October 23, 2012, 11:13:29 PM »

Nice to know there is at least one other crazy antenna experimenter out there - they may name a ward after us!

I have not tried a vertically polarized delta loop yet (no trees), but I recently got some crappie poles so the time is near.
I hear LOTS of guys using delta loops on PSK31 and they seem to work really well.
The delta loop is penciled in my schedule, together with a vertical Moxon, both hanging off the crappie pole.
For the Moxon idea I will have a couple of fishing poles angled from a bit below the top of the crappie pole to give a horizontal span.

When you said talking trees, for a moment, I remembered the 'Nam experiments with clamping a coil around trees for comms.
I don't think it worked very well.

NCL2000, Matchbox, both sweet bits of gear.
I was too poor in those days to score that type of gear, but at least I got to look at them in magazines.
You've got me all nostalgic now - I think I might go into the workshop and build a matchbox clone.

One antenna I found which works really well (here at least) is an old style single wire windom with a counterpoise.
I fed the single vertical wire with a remote atu at ground level, and that sucker worked GREAT from 40m to 6m.
The pattern would have been all over the shop on the higher bands, but it still pumped out a good signal.

Keep experimenting,  73 - Rob
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W5DXP
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« Reply #33 on: October 24, 2012, 05:18:20 AM »

Don't sweat it, the most accurate thing one can say about their antenna, is that at my qth this works better than that.

There's a discussion on one of the other ham groups that asks the question: How much of the vertical's ground wave escapes ground attenuation and makes it into the far field? NEC4 seems to be shedding some light on that subject. Perhaps that explains the difference between NEC2 simulations and the performance of verticals? One would think that, on a mountain top, much of the ground wave would escape to the far field and eventually encounter the ionosphere at the lowest possible elevation angles. Maybe the earth is not flat after all.Smiley
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73, Cecil, www.w5dxp.com
The purpose of an antenna tuner is to increase the current through the radiation resistance at the antenna to the maximum available magnitude resulting in a radiated power of I2(RRAD) from the antenna.
RFRY
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Posts: 317


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« Reply #34 on: October 24, 2012, 06:01:42 AM »

There's a discussion on one of the other ham groups that asks the question: How much of the vertical's ground wave escapes ground attenuation and makes it into the far field? NEC4 seems to be shedding some light on that subject. ... One would think that, on a mountain top, much of the ground wave would escape to the far field and eventually encounter the ionosphere at the lowest possible elevation angles.

Unfortunately, NEC defines the far-field to exist only at an infinite
distance over an infinite, flat ground plane.  I think this has mislead most
NEC operators, and evaluators of NEC far-field calculations.

Antenna engineering texts show that the boundary between the near and the
far fields is related to the greatest physical dimension of the radiator
with respect to wavelength.  In the case of the 1/4-wave monopole on 1.85
MHz in my NEC model, that boundary is defined as 2L2/lambda, or about 20
meters from the radiator.

The fields in my NEC4 plots were calculated for a horizontal distance of 100
meters, so they are, in fact, far fields of the antenna.  Note also that in the plots
the fields for earth conductivity of 1 mS/m are less than 3 dB below the fields for
sea water conductivity.  Probably this reality is not very intuitive to many.

Now, to the questions above:

It isn't the groundwave that reaches the ionosphere, but the low angle
radiation shown in my NEC plots, for the fields close to a monopole.
Those fields are actually space waves, and for those low angles can
provide the greatest range for single-hop skywave coverage.

The part of the radiated, v-pol wavefront that contacts the earth (the
groundwave) penetrates the earth to some depth, causing earth currents to
flow in the horizontal plane, in the direction of propagation from the
transmit antenna.  These currents are lost to the groundwave radiation just
above the surface of the earth, and are the reason that the groundwave decays
at a rate greater than 1/r.  So after some distance of travel along the surface of
the earth, the groundwave field falls essentially to zero.

However that extreme loss does not occur sufficiently close to the radiator,
which is the reason that AM broadcast stations and hams on 160m can have
substantial groundwave coverage in the day time.

Valleys and mountains can affect the fields radiated by a monopole, but
probably not as severely as expected.  As shown in the NEC plots, the
relative fields for low vertical angles are very high, as they would be even
for negative vertical angles looking down from a mountain top.

I think that the Denver AM stations have no great, general coverage issues
due to their proximity to the mountains there to the West.

Too bad that a terrain-elevation-based propagation program apparently does
not exist for freqs below VHF.

http://i62.photobucket.com/albums/h85/rfry-100/Monopole_Surf_Wv_Compare.jpg

R. Fry
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W8JI
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Posts: 9296


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« Reply #35 on: October 24, 2012, 07:00:32 AM »

Nope, it was horizontal. On paper, the beam should be better, but in on the air tests, the vertical was better 2 out of 3 contacts. The Butternut is a 3/4 wave vertical on 10 meters so in theory the beam should have out performed it; but it didn't for DX.

That is insane!


Nope, happens to me all the time.
A local friend has a 3 element yagi up 30 feet on 20m, and I beat him to the DX most times.
The difference is the angle of takeoff.
I hear Europe come in on the gray line about 30 minutes before he does, due to my vertical's low angle performance.
Once the skip comes in on a higher angle he is good to go, and does pretty well, but not that much better than me.

Much of the time when we compare antennas, it is more about what is wrong with the reference than what is special with the magically better antenna.

I have open fields with pasture, have a few feet of darker top dirt instead of just red clay, and I'm on a slight ridge. While I have no problems at all working DX with a ground mounted vertical, there is clearly never a comparison to any of my Yagi antennas. The ONLY band a vertical works exceptionally well on is 160 meters, and to a lesser extent a vertical is competitive on 80 meters.

Here on 160, a dipole at 300 feet roughly ties a 200 ft vertical. The dipole is maybe a 3 dB better, but off the dipole ends the vertical is 10-15 dB better.

On 80 meters, a dipole at 160 feet is just a few dB weaker than a 4 square. The dipole is about 3 dB better than a 1/4 wave vertical with good ground system for DX broadside to the dipole, and the dipole smokes the vertical for closer stuff. Off the dipole ends,  the vertical is better.

On 40 meters a 1/4 wave vertical with 60 radials is consistently about 10-12 dB down from a 3-element Yagi at 90 feet.
The difference between a 4 square of 1/4 wave verticals and a stack of two 40M Yagi's is phenomenal.

On 20 meters, a 20 meter monoband vertical with good ground is about 15 dB down from a 24 foot boom monoband Yagi at 70 feet height. This is VERY consistent.

On the other hand I can compare my verticals to other people in the Atlanta area who have beams, and beat them.

The problem is obviously not that my verticals are "special", but rather how other locations, installations, or antennas are NOT as good.

There is always a reason why things work the way they work, and almost all of the time when something doesn't work according to theory it is because we overlooked something or did something wrong. The last thing I do is compare my antennas to antennas other people are using at their entirely different location. That is about worthless.

Another very common problem in comparisons, besides normal environmental clutter and how the antenna is actually built or installed, is comparing between antennas people have jammed into a small location. There can be considerable pattern distorting interactions even at more than 1 wavelength spacing. 250-500 feet is close enough to seriously affect pattern on 160 meters, and stuff that distance can even affect pattern on ten meters.

I would never form any conclusion comparing to an antenna off-site.

73 Tom
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STAYVERTICAL
Member

Posts: 875




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« Reply #36 on: October 24, 2012, 12:54:12 PM »


Unfortunately, NEC defines the far-field to exist only at an infinite
distance over an infinite, flat ground plane.  I think this has mislead most
NEC operators, and evaluators of NEC far-field calculations.

Antenna engineering texts show that the boundary between the near and the
far fields is related to the greatest physical dimension of the radiator
with respect to wavelength.  In the case of the 1/4-wave monopole on 1.85
MHz in my NEC model, that boundary is defined as 2L2/lambda, or about 20
meters from the radiator.

The fields in my NEC4 plots were calculated for a horizontal distance of 100
meters, so they are, in fact, far fields of the antenna.  Note also that in the plots
the fields for earth conductivity of 1 mS/m are less than 3 dB below the fields for
sea water conductivity.  Probably this reality is not very intuitive to many.

Now, to the questions above:

It isn't the groundwave that reaches the ionosphere, but the low angle
radiation shown in my NEC plots, for the fields close to a monopole.
Those fields are actually space waves, and for those low angles can
provide the greatest range for single-hop skywave coverage.

The part of the radiated, v-pol wavefront that contacts the earth (the
groundwave) penetrates the earth to some depth, causing earth currents to
flow in the horizontal plane, in the direction of propagation from the
transmit antenna.  These currents are lost to the groundwave radiation just
above the surface of the earth, and are the reason that the groundwave decays
at a rate greater than 1/r.  So after some distance of travel along the surface of
the earth, the groundwave field falls essentially to zero.

However that extreme loss does not occur sufficiently close to the radiator,
which is the reason that AM broadcast stations and hams on 160m can have
substantial groundwave coverage in the day time.

Valleys and mountains can affect the fields radiated by a monopole, but
probably not as severely as expected.  As shown in the NEC plots, the
relative fields for low vertical angles are very high, as they would be even
for negative vertical angles looking down from a mountain top.

I think that the Denver AM stations have no great, general coverage issues
due to their proximity to the mountains there to the West.

Too bad that a terrain-elevation-based propagation program apparently does
not exist for freqs below VHF.

http://i62.photobucket.com/albums/h85/rfry-100/Monopole_Surf_Wv_Compare.jpg

R. Fry

Very interesting stuff - thanks for that information.

73 - Rob
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W5WSS
Member

Posts: 1744




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« Reply #37 on: October 24, 2012, 05:04:59 PM »

I work allot with verticals these days.....Got to say it is not difficult to build a quarter wave for 20m to 10m.

That is to say not too huge but rather is more feasible for the average ham.

I have used large arrays and lived the dream. I know the difference as Tom is relaying.

Lately I had occasion here to build quarter wave mono band verticals.

The simple little antenna has a place a niche close to ground that offers excellent return for my cost to build was $20.

the whole thing made of wire.

#14 black insulated copper Three pieces(or more) of wire cut exactly the same length.

Bring to the center and drive two or more with the shield of your coaxial cable slope downward 60 degrees but watch match as you slope.

Feed the one going upward with center conductor.

Weather proof the feedline connections

I used an so239

Attach an insulator at the tip and rope and hang the thing at some elevated height.

Do the rope and insulator to the 2 or more shield driven sloped elevated radials and anchor in the final position.

Bring the rope fully to the ground for strain relief along the wire.

I used a small crappy rod and made one cast and was done the antenna rested at 22 ft base height for the 15m version and the match was as expected for an antenna that slope radials help better match to 50 ohm coax.

The feedline looks into low loss condition and the antenna works as good as a quarter wave is capable cheap and fun

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KA7NIQ
Member

Posts: 258


WWW

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« Reply #38 on: October 24, 2012, 08:31:57 PM »

I work allot with verticals these days.....Got to say it is not difficult to build a quarter wave for 20m to 10m.

That is to say not too huge but rather is more feasible for the average ham.

I have used large arrays and lived the dream. I know the difference as Tom is relaying.

Lately I had occasion here to build quarter wave mono band verticals.

The simple little antenna has a place a niche close to ground that offers excellent return for my cost to build was $20.

the whole thing made of wire.

#14 black insulated copper Three pieces(or more) of wire cut exactly the same length.

Bring to the center and drive two or more with the shield of your coaxial cable slope downward 60 degrees but watch match as you slope.

Feed the one going upward with center conductor.

Weather proof the feedline connections

I used an so239

Attach an insulator at the tip and rope and hang the thing at some elevated height.

Do the rope and insulator to the 2 or more shield driven sloped elevated radials and anchor in the final position.

Bring the rope fully to the ground for strain relief along the wire.

I used a small crappy rod and made one cast and was done the antenna rested at 22 ft base height for the 15m version and the match was as expected for an antenna that slope radials help better match to 50 ohm coax.

The feedline looks into low loss condition and the antenna works as good as a quarter wave is capable cheap and fun


I have been hearing a few of these things http://w8amz.com/W8AMZ_VERTICALS_Page.html on 40 lately.
I think he builds them for other bands too. They only have 2 radials, but they are elevated.

I am down in Florida, and talked to a guy using one of these out in Oklahoma.
He had it hung from a 55 ft tree limb. He has only had it a few months, but he said he likes it. I suggested maybe he add 2 more radials to it, and he said he might do just that.
These things are quite inexpensive, like under 50 dollars for the 40 meter version, shipped.
Of course, one could always build it for a little less I guess ?
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W8JI
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Posts: 9296


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« Reply #39 on: October 25, 2012, 06:04:10 AM »

I have been hearing a few of these things http://w8amz.com/W8AMZ_VERTICALS_Page.html on 40 lately.
I think he builds them for other bands too. They only have 2 radials, but they are elevated.

I am down in Florida, and talked to a guy using one of these out in Oklahoma.
He had it hung from a 55 ft tree limb. He has only had it a few months, but he said he likes it. I suggested maybe he add 2 more radials to it, and he said he might do just that.
These things are quite inexpensive, like under 50 dollars for the 40 meter version, shipped.
Of course, one could always build it for a little less I guess ?


A two-radial vertical is just barely different than a dipole at the feedpoint. It is actually more a balanced antenna than UNbalanced. As such, it has significant common mode voltage exciting the CM impedance of the shield. (Even four radials behave this way, to a somewhat lesser extent.)

Ask the manufacturer, whoever makes it,  if the two-radial vertical has a good common mode feedline choke.

If the vertical does NOT have a very good common mode choke on the feedline, it is a poor design. It can have nearly as much radiation from the coax as from the antenna itself. It will be feedline length sensitive, feedline grounding sensitive, have unpredictable pattern, and susceptable to common mode issues like RFI and noise ingress.

Common mode is a very serious issue with two radials, and although it diminishes witjh increasing radials does not "nearly go away" without help until 12-20 radials are used.  Even a four radial groundplane can have significant common mode on the mast or feedline!

When you hear someone using a sparse ground on a Marconi pretending it is adequate, ask them how they handled common mode. If they can't answer, or if they say they didn't handle it because the antenna is naturally "unbalanced", then it tells you how well they actually understand antennas.

73 Tom
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W5WSS
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Posts: 1744




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« Reply #40 on: October 25, 2012, 08:04:34 AM »

Yeah ka7niq, it is not a Marconi it is a form of dipole My version uses a common mode choke at the feed point then the feedline runs straight down the rope there is no metal pole and contacts the ground  then routes to the shack entrance for a good distance.

As a extra measure one could incorporate another choke just outside the entry for more common mode attenuation But it is best to properly prevent common mode development at the source the antenna feed point location.

My common mode choking passes my scrutiny as does the antenna performance.

The definition of this antenna is found when we view it as a type of elevated dipole rather than an elevated ground plane because of the elevated sloping radials 2 or more equidistantly distributed placed equal and opposite each other work to help set the feed point impedance and work to cancel horizontal radiation  horizontal lines of electromagnetic wave whilst contributing to vertical radiation  due to sloping through the horizontal and vertical axis adding to the sum of the vertical elements total radiation within the antennas polar pattern

Yes I acknowledge the feed point balance to unbalance difference and treatments for proper feedpoint balance AT the feed point source are remedied with 1:1 common mode attenuation, impedance transformation is not needed..

Another words unwanted development of common mode displacement currents are avoided in the first place isolated and attenuated with my treatment.

A ground plane then is different because of the horizontal orientation of the radials they simply do not contribute to vertical radiation like sloped radials can when working properly, but if or when common mode is allowed to developer then that current can  radiate and slews the otherwise understood pattern development expected from the antenna.proper.

A word about more radials for more common mode attenuation and proper antenna function.

We can, but do not simply co axially feed an naked center conductor with everything peeled off the coaxial line obviously.
It would simply be  a weird behaving active braid in conjunction with the peeled away quarter wave center. But rather avoid that because of common mode displacement currents obeying Kirchhoff's law seeking a conductor for completion and radiating from there to the shack yes a more expensive vertical longwire.

To prevent this

We add the radials to a elevated vertical conductor for the purpose of completing the antenna and the provision of common mode attenuation while doing so we discovered that sloping the elevated radials( as many as you want to incorporate is fine,(build a discone second half if you want) provided they are added evenly to the dividend of the spacial area around the semi circle just adjacent to just underneath and at the feed point. This method will add a second half di to the pole completing this antenna that can equal a dipole in Field strength vertically.and omnidirectional. The radials are equivalent to a split into as many parts of the whole as you want second dipole leg.


In a word add as many radials as you want just install an equal balance of them around the available space for assurance of common mode attenuation, omni directional pattern development, dipole radiation Field strength.and feed point impedance so one will need to look to match the antenna after construction  placed in its position tune  lower and raise if need be. but should be close simply prune the vertical portion.

I purposely made it a little longer than the quarter wave estimate.

Yes all that complicated stuff is involved but need not cost a fortune again $20 bucks and fun.
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